The functional roles of disulfide bonds in the β‐subunit of (Na,K)ATPase as studied by site‐directed mutagenesis

FEBS Letters

Mutoh, Yoshinobu¹  Kawamura, Masaru¹  Noguchi, Shunsuke¹ 

[1] Department Biology, University of Occupational and Environmental Health, Kitakyushu 807, Japan

关键词: (Na;    K)ATPase;    β-Subunit;    Disulfide bond;    Site-directed mutagenesis;   

DOI  :  10.1016/0014-5793(94)80463-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The β-subunit of Torpedo californica (Na,K)ATPase contains seven cysteine residues; one (Cys⁴⁶) is in the single transmembrane segment and the other six (Cys¹²⁷, Cys¹⁵⁰, Cys¹⁶⁰, Cys¹⁷⁶, Cys²¹⁵ and Cys²⁷⁸) are in the extracellular domain and form three highly conserved disulfide bonds. Aβ-subunit mutant with replacement of Cys⁴⁶ by Ser could assemble with the α-subunit, and the resulting αβ-complex was catalytically active. Mutants in which either the N-terminal side or both Cys residues of the Cys¹²⁷-Cys¹⁵⁰ bond were replaced by Ser could also tightly assemble with the α-subunit, but the resulting αβ-complex was catalytically inactive. On the other hand, disruption of either the Cys¹⁶⁰-Cys¹⁷⁶ or Cys²¹⁵-Cys²⁷⁸ bond by substituting the N-terminal side only or both Cys residues with Ser led to a β-subunit that could not assemble with the α-subunit. We conclude that the structure of the β-subunit around the Cys¹⁶⁰-Cys¹⁷⁶ and Cys²¹⁵-Cys²⁷⁸ loops is indispensable for assembly with the α-subunit, whereas the Cys¹²⁷-Cys¹⁵⁰ loop is not essential for assembly but is required for enzyme activity.

【 授权许可】

Unknown